The invention relates to electronic semiconductor devices, and, more particularly, to dielectric structures and fabrication methods for such structures.
The performance of high density integrated circuits is dominated by metal interconnect level RC time delays due to the resistivity of the metal lines and the capacitive coupling between adjacent lines. The capacitive coupling can be reduced by decreasing the relative permittivity (dielectric constant, k) of the dielectric (electrical insulator) between adjacent lines.
Various dielectric materials have been suggested for use in silicon integrated circuits to replace the commonly used silicon dioxide (k about 4.0). The leading candidates are fluorinated silicon dioxide (k about 3.0-4.0), organic polymers such as polyimide, parylene, bis-benzocyclobutene (BCB), amorphous teflon (k about 1.9-3.9), and porous dielectrics such as silicon dioxide based xerogels (k dependent upon pore size and typically 1.3-3.0).
Similarly, decreasing the resistivity of the interconnect metal by substituting copper (or silver) for the commonly used aluminum and tungsten will also reduce the RC time constant.
Copper interconnects typically require a dual inlaid (dual damascene) process for fabrication which uses a first via etch through two dielectric layers followed by a second interconnect trench etch through just the top dielectric. Then the trench and via are filled with copper by blanket deposition plus planarization to remove copper outside of the trench and via; chemical mechanical polishing (CMP) provides the planarization. However, photoresist exposure and development for the trench etch has problems at the vias, and subsequent trench etch can breakthrough the interconnect passivation at the via bottoms.
Thus the current fabrication methods for copper interconnects using CMP processing have manufacturability problems.
The present invention provides a temporary filler for etched vias during dual inlaid interconnect trench processing.
This has the advantages of robust dual inlaid processing.